Automatic aircraft powerplant control

ABSTRACT

An automatic aircraft powerplant control system includes a throttle servo for adjusting a throttle valve via a throttle control linkage. A throttle control lever provides a user input to the throttle servo, and a throttle controller controls the throttle servo for controlling a throttle valve. A dual-redundant propellor servo drive provides propellor control, and a dual-redundant mixture servo drive controls an air-fuel mixture. A first processor and a second processor are communicatively coupled with the dual-redundant propellor servo drive and the dual-redundant mixture servo drive and with each other to provide dual-redundant propellor and mixture control. The throttle control lever provides a single lever for pilot control of aircraft power, and the throttle control configuration is compatible with an auto-land capability.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.63/191,101 entitled “Single Lever Power Control For Piston Aircraft” andfiled on May 20, 2021, which is herein incorporated by reference in itsentirety.

BACKGROUND OF THE INVENTION 1. Field

The disclosed embodiments relate generally to the field of enginecontrols. More specifically, the embodiments relate to singlepower-lever control in piston aircraft.

2. Description of the Related Art

Many types of aircraft powerplant control are known. For example, U.S.Pat. No. 10,604,268 to Lisio et al. discloses auto throttle control forturbo-prop engines including a single lever power throttle to controlthe engine and the propellor. U.S. Pat. No. 9,506,405 to Vos discloses asingle lever power controller for a power generation system, with aprocessor that may include a full authority digital electronic control(FADEC) engine. U.S. Pat. No. 11,085,391 to Hunter et al. discloses athrottle quadrant arrangement that uses a single throttle leverconnected to three rotary-variable-differential transformers (RVDTs),which provide throttle lever commands to a FADEC controller thatdetermines the correct fuel flow and power levels for the turbineengine, and pitch control for the propellor. U.S. Patent ApplicationPublication No. 2017/0017257 to Sparks discloses a single lever powercontrol system for use with variable pitch propellor aircraft, whichuses an H-shaped plate configured for the lever to move in a flight modeand a feather mode.

SUMMARY

This summary is provided to introduce a selection of concepts in asimplified form that are further described below in the detaileddescription. This summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter. Other aspectsand advantages will be apparent from the following detailed descriptionof the embodiments and the accompanying drawing figures.

In an embodiment, an automatic aircraft powerplant control systemincludes a throttle control configuration for controlling a throttle.The throttle control configuration includes a throttle servomechanically coupled with an engine via a throttle control linkage. Thethrottle servo is configured for adjusting a throttle valve via thethrottle control linkage. A throttle control lever is communicativelycoupled with the throttle servo for providing a user input to thethrottle servo. A throttle controller is communicatively coupled withthe throttle servo for controlling the throttle servo. A dual-redundantpropellor servo drive for providing propellor control includes a firstpropellor servo mechanically coupled with the engine via a firstpropellor control linkage. The first propellor servo is configured foradjusting a propellor governor setting of the engine. A second propellorservo is mechanically coupled with the engine via a second propellorcontrol linkage. The second propellor servo is configured as a backup tothe first propellor servo for adjusting the propellor governor settingof the engine. A dual-redundant mixture servo drive for controlling anair-fuel mixture includes a first mixture servo mechanically coupledwith the engine via a first mixture control linkage. The first mixtureservo is configured for providing a mixture control output to the enginevia the first mixture control linkage. A second mixture servo ismechanically coupled with the engine via a second propellor controllinkage. The second mixture servo is configured for providing themixture control output to the engine via the second mixture controllinkage.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Illustrative embodiments are described in detail below with reference tothe attached drawing figures, which are incorporated by reference hereinand wherein:

FIG. 1 is a block diagram illustrating different optional components foran automatic aircraft powerplant control system, in an embodiment;

FIG. 2 is a schematic diagram showing a throttle-control configuration,in an embodiment;

FIG. 3 is a schematic diagram showing a propellor-control configuration,in an embodiment;

FIG. 4 is a schematic diagram showing another embodiment of apropellor-control configuration;

FIG. 5 is a schematic diagram showing another embodiment of amixture-control configuration, in an embodiment;

FIG. 6 is a schematic diagram showing another embodiment of amixture-control configuration;

FIG. 7 is a schematic diagram showing yet another embodiment of amixture-control configuration;

FIG. 8 is a schematic diagram showing an embodiment for providingautomated mixture control and optionally automated propellor control;

FIG. 9 is a schematic diagram showing a combination throttle-control,propellor-control, and mixture-control configuration, in an embodiment;

FIG. 10 is a schematic diagram showing another embodiment of acombination throttle-control, propellor-control, and mixture-controlconfiguration;

FIG. 11 is a schematic diagram showing yet another embodiment of acombination throttle-control, propellor-control, and mixture-controlconfiguration;

FIG. 12 is a schematic diagram showing still another embodiment of acombination throttle-control, propellor-control, and mixture-controlconfiguration;

FIG. 13 is a schematic diagram showing an embodiment for use withautomated mixture control and automated propellor control;

FIG. 14 is a flow diagram of a power-up sequence for an aircraftequipped with an auto-start function, in an embodiment;

FIG. 15A is a flow diagram of a first portion of an auto-start sequencefor an aircraft equipped with an auto-start function;

FIG. 15B is a flow diagram of a second portion of the auto-startsequence of FIG. 15A;

FIG. 16 is a flow diagram of aircraft operational modes, in anembodiment;

FIG. 17 is a flow diagram of auto-mixture operational control, in anembodiment;

FIG. 18 is a flow diagram of an auto-propellor operational control, inan embodiment; and

FIG. 19 is a flow diagram of an auto-throttle operational control, in anembodiment.

The drawing figures do not limit the invention to the specificembodiments disclosed and described herein. The drawings are notnecessarily to scale, emphasis instead being placed upon clearlyillustrating the principles of the invention.

DETAILED DESCRIPTION

The following detailed description references the accompanying drawingsthat illustrate specific embodiments in which the invention can bepracticed. The embodiments are intended to describe aspects of theinvention in sufficient detail to enable those skilled in the art topractice the invention. Other embodiments can be utilized and changescan be made without departing from the scope of the invention. Thefollowing detailed description is, therefore, not to be taken in alimiting sense. The scope of the invention is defined only by theappended claims, along with the full scope of equivalents to which suchclaims are entitled.

In this description, references to “one embodiment,” “an embodiment,” or“embodiments” mean that the feature or features being referred to areincluded in at least one embodiment of the technology. Separatereferences to “one embodiment,” “an embodiment,” or “embodiments” inthis description do not necessarily refer to the same embodiment and arealso not mutually exclusive unless so stated and/or except as will bereadily apparent to those skilled in the art from the description. Forexample, a feature, structure, act, etc. described in one embodiment mayalso be included in other embodiments, but is not necessarily included.Thus, the technology can include a variety of combinations and/orintegrations of the embodiments described herein.

Embodiments described herein provide automatic control of systemsrelated to aircraft power generation. For example, embodiments provideautomatic control of a throttle quadrant. The automatic control systemis configured to provide automated control of three thrust-relatedaircraft functions: 1) engine power, 2) propellor speed and pitch, and3) mixture of fuel and air (i.e., the “fuel-air mixture”). In someembodiments, automatic control is provided that enables the use of asingle power lever with a controller to operate more than one of thesethree thrust-related aircraft functions. For example, embodimentsdescribed herein provide a throttle control system that enable a pilotto control the speed and thrust of a piston aircraft via a single powerlever. In embodiments, a hybrid electro-mechanical mixing assembly isprovided that enables a single, full-time-use power lever to providecontrol outputs to the engine for power, propellor speed and pitch, andfuel-air mixture. Secondary levers may be retained with the power leverin some embodiments to provide back-up control in the event of a failureor malfunction with the control system.

Advantages of the automated engine controls or single power leverinclude reduced pilot workload and simplified aircraft management.Conventional systems that provide a throttle control function, such as athree-servo control system, are large, complex, heavy, and expensive,making them practical only for larger aircraft such as turbopropaircraft. Embodiments described herein provide simpler and smallersystems compared to conventional throttle control systems, which makesfeasible their use in piston aircraft. However, the systems disclosedherein could be used in other types of aircraft without departing fromthe scope hereof.

FIG. 1 is a block diagram illustrating exemplary arrangements for anautomatic aircraft powerplant control system 100 for piston aircraft.Automatic aircraft powerplant control system 100 includes a throttle,which is a power throttle configured to provide control of an enginethrottle valve based on a position of the pilot's power control lever.The engine throttle valve controls the amount of fuel-air mixture to theengine. In embodiments, the throttle is configured as a throttle controlthat includes a single servo capable of back driving an existingthrottle control lever for controlling the throttle valve. Control ofthe propellor speed and pitch, as well as the mixture of fuel and air,may in some embodiments be coupled with throttle control, orindependently controllable in other embodiments, as further describedbelow. Different variations of automatic aircraft powerplant controlsystem 100 may be accomplished with mechanical or hybridelectro-mechanical linkages, as further described below in connectionwith the drawing figures.

Throttle Control

FIG. 2 is a schematic diagram showing an exemplary throttle-controlconfiguration 200 having a single servo drive. A throttle controllinkage 114 provides a mechanical linkage between a power control lever111, a throttle control servo 126, and an engine 115. Throttle controllinkage 114 is for example a push-pull cable, a pushrod, a linkage, orsome combination of these. Engine 115 is for example a piston-typeengine. Linkage 114 provides a direct mechanical coupling such thatthrottle control servo 126 can back drive power control lever 111, andpower control lever 111 can manually override throttle control servo126.

A throttle controller 120 is configured to control throttle controlservo 126. For example, throttle controller 120 may be embodied as acontrol board having one or more of a printed circuit board (PCB), acomputer, a microcontroller, a microprocessor, or a programmable logiccontroller (PLC), having a memory, including a non-transitory medium forstoring software/firmware, and a processor for executing instructions ofthe software/firmware. Throttle controller 120 includes control (COM)and monitoring (MON) channels to and from throttle control servo 126 andan avionics bus 162 of the aircraft. Throttle controller 120 isconfigured for controlling throttle control servo 126 based on inputsfrom avionics bus 162. Inputs include but are not limited to a throttleposition, various aircraft and engine parameters (e.g., cylinder-headtemperature, exhaust gas temperatures, altitude, airspeed, outside airtemperature, manifold pressure, propellor speed).

A mechanical mixer 142 is configured for mixing the throttle servo 126input to the mechanical input from the power control lever 111 to engine115. In the embodiments disclosed herein, mechanical mixer 142 may beremote located anywhere between the propellor control lever 113 andengine 115 and either forward or aft of a firewall, which providesflexibility for determining where to locate mechanical mixer 142, andallows for rigging to be accomplished on a bench prior to installationrather than onboard the aircraft. For example, mechanical mixer 142 doesnot need to be installed at the throttle lever, but may instead be inthe engine compartment or mounted externally to the engine.

Propeller Control

Propeller control is used to adjust a propellor governor setting of theaircraft's engine, which maintains a desired propellor speed inrotations-per-minute (RPM) (e.g., 2400-RPM, 2500-RPM, 2600-RPM, etc.)across variable power settings.

FIG. 3 is a schematic diagram showing a single-servo propellor drive 300coupled with electronic control for controlling propellor speed. Itemsenumerated with like numerals in the various figures are the same orsimilar and their description may not be repeated accordingly.

As depicted in FIG. 3, a propellor lever 113 is configured to acceptuser input for propellor control. A propellor-control servo 156 is usedto provide control of the propellor governor via propellor-control cable112. A propellor controller 160 is configured to provide electroniccontrol of propellor-control servo 156. Propeller-control cable 112mechanically couples propellor-control servo 156 to engine 115 forchanging the propellor governor setting, which is used to change thepropellor pitch, and thus the propellor speed for a given power outputfrom engine 115. In other words, propellor-control servo 156 is used toprovide control of the propellor governor via propellor-control cable112.

Propeller controller 160 may be embodied as a control board having oneor more of a printed circuit board (PCB), a computer, a microcontroller,a microprocessor, or a programmable logic controller (PLC), having amemory, including a non-transitory medium for storing software/firmware,and a processor for executing instructions of the software/firmware.

The controllers described herein, including propellor controller 160,are not limited by the materials from which they are formed or theprocessing mechanisms employed therein and, as such, may be implementedvia semiconductor(s) and/or transistors (e.g., electronic integratedcircuits (ICs)), and so forth. It should also be appreciated that thediscussed functions and methods performed by the controllers describedherein may be performed by other processors (e.g., within a flightcomputer).

Propeller controller 160 includes control (COM) and monitoring (MON)channels to and from propellor-control servo 156 and avionics bus 162 ofthe aircraft. Inputs from avionics bus 162 to propellor controller 160include but are not limited to a throttle position, an RPM command toset a propellor speed or a range of propellor speeds, as well as variousaircraft parameters and various engine parameters (e.g., aircraftattitude, airspeed, manifold pressure, cylinder-head temperature, andengine exhaust gas temperature).

A mechanical mixer 144 is configured for mixing the propellor servo 156input to the mechanical input from the propellor control lever 113 toengine 115. In the embodiments disclosed herein, mechanical mixer 144may be remote located anywhere between the propellor control lever 113and engine 115 and either forward or aft of a firewall, which providesflexibility for determining where to locate mechanical mixer 144, andallows for rigging to be accomplished on a bench prior to installationrather than onboard the aircraft. For example, mechanical mixer 144 doesnot need to be installed at the propellor governor, but may instead bein the engine compartment or mounted externally to the engine.

FIG. 4 is a schematic diagram showing a single-servo propellor drive 400coupled with electronic control for controlling propellor speed andhaving a back-up electro-mechanical advance. The back-upelectromechanical advance has no mechanical link to the throttle lever.Instead, it utilizes a propellor RPM solenoid 154 that is configured toforce the propellor to a high-speed state (i.e., the high RPM state) viapropellor-control cable 112. An emergency advance switch 158 iselectronically coupled with propellor RPM solenoid 154, which enablesthe pilot to select the high RPM state of the propellor for theremainder of the flight. In embodiments, propellor RPM solenoid 154 maybe used to change the mechanical scheduling of the propellor viapropellor-control cable 112. Propeller RPM solenoid 154 may be activatedby the pilot via a switch or rheostat, such as a propellor RPM switchlocated in the cockpit. The propellor RPM switch is communicativelycoupled with propellor RPM solenoid 154 for receiving a pilot input,which enables the pilot to switch between low-speed (i.e., low RPM)setting and a high-speed (i.e., high RPM) setting for changing a speedof the propellor. The low RPM and high RPM propellor speed settings mayeach include a range of propellor speeds. Alternatively, an automatedelectronic control (e.g., from the aircraft's avionics system) may beused to automatically activate the RPM adjustment via propellor RPMsolenoid 154 (e.g., during a cruise phase of flight to reduce propellornoise). In embodiments, propellor RPM solenoid 154 causes a fineadjustment of propellor governor control.

In another embodiment, a dual-redundant servo drive 350 with electroniccontrol is provided for controlling propellor speed (see FIG. 1). Withthis option there is no mechanical link to the propellor control lever.In embodiments, a first propellor servo 191 and a second propellor servo192 are configured to provide the dual-redundant servo drive 350 forpropellor control of FIG. 1. In embodiments, a first mixture servo 193and a second mixture servo 194 are configured to provide thedual-redundant drive 550 for mixture control of FIG. 1. Dual-redundantservo drive 350 and dual redundant servo drive 550 are further describedbelow in connection with FIG. 11. Without departing from the scopehereof, dual-redundant servo drive 350 for propellor control may beprovided without providing dual-redundant servo drive 550 for mixturecontrol (not shown).

Mixture Control

Control of the correct ratio of fuel to air in the fuel-air mixture isimportant for proper operation of an aircraft engine. A “full rich”setting indicates the highest ratio of fuel to air for the lowestoperating altitude of the aircraft (e.g., typically sea level). As theaircraft's altitude increases while climbing, the density of airdecreases causing the fuel-to-air ratio to become richer. To compensate,the mixture is “leaned” via the mixture control, which decreases fuelflow to match the decreased air density at higher altitudes. Conversely,while the aircraft is descending from high altitude, the fuel-airmixture is enriched by increasing fuel flow via the mixture control. Asdescribed below in connection with FIGS. 5-8, at least four options maybe employed to provide mixture control.

FIG. 5 is a schematic diagram showing a single-servo mixture drive 500coupled with electronic control for controlling the fuel-air mixture.Single-servo mixture drive 500 includes mixture control servo 146 withina mechanical mixer 140 (e.g., a mixing box). A mixture control output isprovided to engine 115 for engine mixture control via a linkage 145,which is a mechanical linkage such as a push-pull cable or a pushrod.Mechanical mixer 140 is configured to mix input from the mixture controlservo 146 with mechanical input from a mixture lever 131 to engine 115.In the embodiments disclosed herein, mechanical mixer 140 may be remotelocated anywhere between mixture lever 131 and engine 115 and eitherforward or aft of a firewall, which provides flexibility for determiningwhere to locate mechanical mixer 140, and allows for rigging to beaccomplished on a bench prior to installation rather than onboard theaircraft. For example, mechanical mixer 140 may be installed in theengine compartment or mounted externally to the engine.

In embodiments, mechanical mixer 140, mechanical mixer 142, andmechanical mixer 144 comprise the same or similar type of deviceconfigured to mechanically mix an input received from a servo (e.g.,mixture control servo 146, throttle control servo 126, and propellorcontrol servo 156, respectively) with an input received from a manualcontrol lever (e.g., mixture lever 131, power control lever 111, andpropellor control lever 113) to provide proper control at engine 115,including back-drive of each manual control lever when the respectiveservo is active.

Single-servo mixture drive 500 employs a mixture controller 130 tocontrol mixture control servo 146 for implementing fully automatedmixture control. Mixture controller 130 may be embodied as a controlboard having one or more of a printed circuit board (PCB), a computer, amicrocontroller, a microprocessor, or a programmable logic controller(PLC), having a memory, including a non-transitory medium for storingsoftware/firmware, and a processor for executing instructions of thesoftware/firmware. Mixture controller 130 includes control (COM) andmonitoring (MON) channels to and from mixture control servo 146 and anavionics bus 162 of the aircraft. Mixture controller 130 is configuredfor controlling mixture control servo 146 based on inputs from avionicsbus 162. Inputs include but are not limited to a throttle position,various aircraft and engine parameters (e.g., cylinder-head temperature,exhaust gas temperatures, altitude, outside air temperature, manifoldpressure, propellor speed). In certain embodiments, mixture controller130 engages a boost solenoid based on barometric pressure and operatingconditions of engine 115 provided via avionics bus 162. For example,this may be used to allow for a reduced mixture at maximum power forhigh altitude take-off and climb.

In certain embodiments, mixture control servo 146 comprises a back-drivecapability that is configured to back drive an existing mixture controllever onboard the aircraft. Optionally, the back-driving capability maybe disengaged to allow for pilot manual control via a mixture lever 131,in which linkage 145 provides a direct mechanical linkage with mixturelever 131. In the event of a failure or malfunction of mixture control,mixture lever 131 enables backup pilot mixture control and manualleaning of the fuel-air mixture via linkage 145. In case of a servomalfunction, the servo malfunction may be mechanically over-ridden bythe pilot to advance the mixture to full rich.

FIG. 6 is a schematic diagram showing an automated single-servo mixturedrive 600 with a full-override option that is configured to provide afully automatic fuel-air mixture to engine 115 via linkage 145 withoutthe use of mixture lever 131. Automated single-servo mixture drive 600includes electronic control via mixture controller 130 of mixturecontrol servo 146 and a mixture full-override device 147. Mixturefull-override device 147 is for example a servo or solenoid. Undernormal operating conditions, mixture control servo 146 is configured formixing fuel and air within mechanical mixer 140 as with single-servomixture drive 500 of FIG. 5. However, a max-mixture switch 149 may beused by the pilot to activate mixture full-override device 147, whichoverrides mixture control servo 146 to provide a full-rich mixture toengine 115 for the remainder of the flight.

Override of a servo malfunction may be accomplished via one of thefollowing options. Optionally, a button is provided that enables thepilot to select a “full rich” mode in which a solenoid is used toover-ride the single-servo mixture drive and force the mixture to a fullrich position. This option may be performed using automated single-servomixture drive 600 of FIG. 6, for example. In another option, adual-redundant servo drive 550 (see FIG. 11) is provided, in which dualservo control is used with monitoring to ensure proper mixture control.

FIG. 7 is a schematic diagram showing an emergency advance mixtureconfiguration 700, which includes an electro-mechanical emergencyadvance option for controlling the fuel-air mixture. In operation, thepilot manipulates the mixture normally via mixture lever 131 untilemergency control is needed. As with single-servo mixture drive 500 ofFIG. 5, the mixture control output is provided to engine 115 for enginemixture control via linkage 145. In emergency advance mixtureconfiguration 700, a mixture input 148A is provided (e.g., via avionics)to mixture boost solenoid 148, which is used to adjust the fuel-airmixture for auto-land or other emergency situations. For example,mixture input 148A may include a mixture boost command (e.g., “000”),which is sent to mixture boost solenoid 148 to drive maximum mixturesettings for emergency or back-up operations. This allows for themixture to be placed into the full-rich state for the remainder of theflight (e.g., when using an auto-land operation). Alternatively, theboost solenoid may be engaged automatically as a back-up feature. Forexample, if the pilot forgets to advance the mixture, the boost solenoidmay be engaged based on barometric pressure and operating conditions ofengine 115.

FIG. 8 is a schematic diagram showing a FADEC mixture-controlconfiguration 800 to automatically control the fuel-air mixture viadual-redundant channels communicatively coupled with a FADEC engine 815.In configuration 800, the FADEC provides digital control, while engine815 performs the mixing. A first channel 871 provides independentcontrol and monitoring paths between FADEC engine 815 and a fuel-airmixture device within FADEC engine 815, and a second channel 872provides independent control and monitoring paths between FADEC engine815 and the fuel-air mixture device.

In another embodiment, a dual-redundant servo drive 550 with electroniccontrol is provided for controlling the air-fuel mixture (see FIG. 11).With this option there is no mechanical link to the mixture lever. Thisconfiguration is intended for use with a full authority digitalelectronic control (FADEC) engine. For example, FIG. 11 shows anembodiment having first mixture servo 193 and second mixture servo 194for providing mixture control. Dual servo control is used withmonitoring to ensure proper mixture control.

Combination Embodiments

Depending on a specific type of piston or other engine type in whichautomatic aircraft powerplant control system 100 of FIG. 1 is employed,different arrangements of propellor control and mixture control may becoupled with the throttle. The different arrangements take advantage ofvarious options for propellor control and various options for fuel-airmixture control. The different arrangements may be accomplished viaspecific combinations of mechanical assemblies, solenoid valves, and/orelectro-mechanical servos. Additionally, the different arrangements ofautomatic aircraft powerplant control system 100 are configured foradding onto existing engines such that certification of the engine isnot affected. Below are some non-limiting examples.

FIG. 9 is a schematic diagram showing an automatic aircraft powerplantcontrol system 900 comprising throttle-control configuration 200 of FIG.2, single-servo propellor drive 300 of FIG. 3, combined withsingle-servo mixture drive 500 of FIG. 5. System 900 combinesindependent engine controls to provide full automation of engine controlthroughout all phases of aircraft flight.

FIG. 10 is a schematic diagram showing an automatic aircraft powerplantcontrol system 1000, which includes throttle-control configuration 200of FIG. 2, single-servo propellor drive 300 of FIG. 3, combined withautomated single-servo mixture drive 600 of FIG. 6. Power control lever111 provides a single lever for a pilot to control the throttle,propellor, and air-fuel mixture. As described above in connection withFIG. 3, emergency-advance switch 158 enables the pilot to select thehigh RPM state of the propellor for the remainder of the flight. Asdescribed above in connection with FIG. 6, max-mixture switch 149 may beused by the pilot to activate mixture full-override device 147, whichoverrides mixture control servo 146 to provide a full-rich mixture toengine 115 for the remainder of the flight.

FIG. 11 is a schematic diagram showing an automatic aircraft powerplantcontrol system 1100 in which the fuel-air mixture and the propellor arecontrolled automatically for use with a non-FADEC engine. Inembodiments, dual-redundant servo drive 350 for propellor control iscombined with dual-redundant servo drive 550 for mixture control. Forexample, dual-redundant servo drive 350 uses first propellor servo 191and second propellor servo 192 to provide dual electronic control ofpropellor speed, and dual-redundant servo drive 550 uses first mixtureservo 193 and second mixture servo 194 to provide mixture control. Aswitch or selector (e.g., propellor RPM switch 152) may be used toselect the preferred cruise propellor speed. Power control lever 111provides a single lever for a pilot to control the aircraft power basedon a position of power control lever 111.

Propeller control is determined automatically based on a throttleposition 173 (e.g., a position of power control lever 111) and aircraftand engine parameters (manifold pressure, altitude, attitude, airspeed,etc.) via redundant dual-channel processors. As depicted in FIG. 11, theredundant dual-channel processors include a first processor 171 for afirst channel and a second processor 172 for a second channel. Avionicsbus 162 provides inputs to each of the first and second processors 171,172, including for example, throttle control commands, cylinder-headtemperature (CHT) feedback, engine exhaust gas temperature (EGT)feedback, propellor speed, and fuel flow. Throttle position 173 isprovided as an input signal to the processors 171, 172 from a positionsensor (e.g., a rotary variable differential transformer (RVDT)) basedon a position of power control lever 111. Propeller RPM switch 152provides input signals for low or high propellor speed ranges to theprocessors 171, 172.

In certain embodiments, output signals from first and second processors171, 172 are sent independently to dual-redundant propellor servos,namely first propellor servo 191 and second propellor servo 192, toprovide propellor control. In some embodiments, output signals fromfirst and second processors 171, 172 are sent independently todual-redundant mixture servos, namely first mixture servo 193 and secondmixture servo 194, to provide mixture control.

A first bus 181 and a second bus 182 enable cross-communication betweenfirst and second processors 171, 172 for channel-to-channel monitoring.Redundant control channels and processors 171, 172 are configured toprovide a safe-mode for controlling the fuel-air mixture after anysingle failure. Automatic aircraft powerplant control system 1100enables simple throttle control implementation compatible with auto-landcapability.

FIG. 12 is a schematic diagram showing an automatic aircraft powerplantcontrol system 1200, which includes throttle-control configuration 200of FIG. 2, single-servo propellor drive 300 of FIG. 3, combined withFADEC mixture-control configuration 800 of FIG. 8. In an alternativeembodiment, dual-redundant servo drive 350 of FIG. 11 is provided inplace of single-servo propellor drive 300, whereby first propellor servo191 and second propellor servo 192 provide dual electronic propellorcontrol, which is combined with FADEC engine 815 of FIG. 8 for providingmixture control. A switch or selector may be used to select thepreferred cruise propellor speed via the propellor controller.

FIG. 13 is a schematic diagram showing an automatic aircraft powerplantcontrol system 1300 in which throttle-control configuration 200 of FIG.2 is combined with FADEC mixture-control configuration 800 of FIG. 8.System 1300 relies on FADEC engine 815 to provide both propellor controland mixture control. Power control lever 111 provides a single lever fora pilot to control the aircraft power since propellor control andmixture control are performed by the FADEC controller of engine 815.

Control Architecture

In some embodiments for controlling the throttle, propellor speed andpitch, and fuel-air mixture from a single power control lever 111, abasic closed loop control structure may be employed, which enables amore generic engine scheduling. For the fuel-air mixture, fuel leaningand economy is maximized based on CHT, EGT or oxygen feedback. Forpropellor control, the closed loop control structure is configured togovern propellor speed, which may include an optional low or selectableRMP mode for operations when a quiet cabin is preferred. A power cablecoupled to the body of power control lever 111 may be maintained formechanical throttle control with a servo for pilot selectable automatedcontrol. This embodiment uses at least one propellor servo and at leastone mixture servo to provide propellor and fuel-air mixture control,respectively. Engine power is mechanically scheduled via a throttle bodybutterfly valve position from the body of power control lever 111, whichmay be similar to existing mechanical fuel injection systems. A safemode provides a “rich enough” mixture for continued safe flight andlanding with normal throttle level control. In the event of a loss ofservo control, a full-rich mixture is used with high RPM propellorcontrol.

In embodiments, a more complex closed loop control structure may beemployed to control the throttle, propellor speed and pitch, andfuel-air mixture from a single power control lever 111. For the fuel-airmixture, fuel metering may be customized based on air flow, instead ofusing butterfly valve position from the body of power control lever 111,which provides a correction for altitude based on air density. A massairflow sensor is used to provide the air flow data. For the fuel-airmixture, fuel leaning and economy is maximized based on CHT and EGTfeedback or oxygen feedback from an oxygen sensor located in thefuel-air mixture. The closed loop control structure is configured togovern propellor speed, which may include an optional low RMP mode foroperations when a quiet cabin is preferred. Instead of having a powercable coupled to the body of power control lever 111, fullthrottle-by-wire control is provided. This requires the addition of athrottle-body butterfly servo and a fuel-metering control servo inaddition to a mixture servo. A dedicated backup power source is providedin case of a main alternator failure combined with a loss of the primarybattery. A safe mode provides a “rich enough” mixture for continued safeflight and landing with normal throttle level control.

Autostart

To start many existing aircraft, the pilot manipulates the throttle andmixture controls with the right hand while engaging the starter switchwith the left hand. Once the engine fires, the pilot must then quicklyreadjust controls to allow the engine to run properly. Embodimentsdescribed herein include an auto-start system for aircraft that providesautomated engine start up by manipulating throttle and mixture control.The pilot initiates startup of the engine using a simple start switch,and then the auto-start system automatically completes all startuptasks, followed by entering a standby mode.

In embodiments, with the aircraft master power switch turned on, thepilot activates the “start” switch (e.g., pushes the start button) whenready to start the engine. When the start button is pressed for thefirst time, an auto-start controller determines the engine state basedon outside air temperature (OAT) and engine CHT, and whether the enginehas excessive fuel in the cylinders. The auto-start controller theninitiates the proper start sequence based on the current engine state.Specifically, a cold start sequence is used if the engine CHT is cold orat ambient temperature; a hot start sequence is used if the engine CHTis greater than a set temperature or if ambient temperatures are hot;or, a flooded start sequence is used when the engine has excessive fuelin the cylinders requiring a special start sequence.

The auto-start controller may be embodied as a control board having oneor more of a printed circuit board (PCB), a computer, a microcontroller,a microprocessor, or a programmable logic controller (PLC), having amemory, including a non-transitory medium for storing software/firmware,and a processor for executing instructions of the software/firmware. Theauto-start controller is communicatively coupled with mixture controland throttle control. The auto-start controller is also communicativelycoupled with the engine start circuit for starting the engine and thefuel pump for controlling fuel flow to the engine.

In certain embodiments, the auto-start system is configured to enablenormal manual starting operation when the auto-start system is turnedoff. In this case, the pilot has normal control of the throttle andmixture, and the start switch is a momentary switch that providesengagement of the start solenoid while the start switch is engaged. Thisprovides a back-up function in case the auto-start system fails.

FIG. 14 is a flow chart showing an exemplary power-up sequence 1400having an auto-start mode. The auto-start mode is provided via theauto-start system described above. Power-up sequence 1400 may beperformed using one of automatic aircraft powerplant control systems900, 1000, 1100, or 1200 described above.

Prior to step 1410, aircraft power is initiated (e.g., the aircraftmaster power switch is turned on), which enables the start button.Otherwise, the start button is effectively locked out.

In a step 1410, a system power-up is accomplished includinginitialization of all system components.

In a step 1420, a self-test is performed once the system is initialized.In an example of step 1420, the auto-start controller performs aself-test of the auto-start system. The self-test may include a seriesof signals (e.g., pings) sent to/from the auto-start controller andvarious aircraft components and sensors to test that they are in anactive or standby state. If the self-test confirms that the auto-startsystem is ready, power-up sequence 1400 proceeds with steps 1430 and1440, followed by step 1450. Otherwise, if the self-test fails, a faultis announced in a step 1425.

Step 1425 provides a fault annunciation. In an example of step 1425, anindicator is activated to indicate that a fault with the self-test hasoccurred. The indicator may include one or more of a light, a sound, ora text display, or crew alerting system annunciation, for example.

In a step 1430, a throttle control is placed into a standby state. In anexample of step 1430, an electronic throttle control reportsavailability and awaits engagement for engine starting while in thestandby state.

In a step 1440, an mixture control standby function is engaged. In anexample of step 1440, mixture controller 130 of FIG. 9 automaticallysets the fuel-air mixture to a predetermined ratio. In another exampleof step 1440, the redundant dual-channel processors 171, 172 of FIG. 11set the fuel-air mixture to the predetermined ratio.

In a step 1450, an auto-start function is engaged. In an example of step1450, the auto-start controller determines the current engine statebased on OAT and engine CHT, and whether the engine has excessive fuelin the cylinders. The auto-start controller then selects the properengine start sequence based on the current engine state and initiatesthe selected engine start sequence. The engine start sequences aredescribed below in FIGS. 15A and 15B. After the auto-start function isengaged in step 1450, the auto-start modes for throttle control andmixture control functions are entered in a step 1460 and a step 1470,respectively.

In step 1460, throttle control enters the auto-start mode. Meanwhile, ina step 1470, mixture control enters the auto-start mode. Specifically,the auto-start controller initiates an engine start sequence based onthe current engine state. For example, a cold-start mode is entered ifthe engine CHT is less than 100° F. and the throttle is not open; ahot-start mode is entered if the engine CHT is greater than 100° F. andthe throttle is not open; or, a flooded-start mode is entered when thethrottle is open. Alternative CHT temperatures may be selected, otherthan 100° F., without departing from the scope hereof. The cold-startmode, hot-start mode, and the flooded-start mode for throttle controland mixture control are further described below in connection with FIGS.15A and 15B.

If the auto-start modes successfully start the engine, step 1460proceeds to a step 1465 to enter throttle control standby, and step 1470proceeds to a step 1475 to engage mixture control. Throttle controlstandby in step 1465 is waiting on flight engagement, in contrast to thestandby state in step 1430, which is waiting on engine start.

In step 1465, the aircraft remains in throttle control standby until theaircraft has reached a predetermined airspeed and altitude. Thenpower-up sequence 1400 proceeds with a step 1490 in which throttlecontrol is engaged. In an example of step 1465, throttle control remainsin standby until the aircraft has reached a predetermined minimumairspeed (e.g., 70-knots or greater), at which point throttle control isengaged in step 1490.

Meanwhile, in step 1475, mixture control is engaged. This is furtherdescribed below for a cold-start, a hot-start, or a flooded-start inconnection with steps 1524, 1554, and 1584 of FIG. 15A, respectively.

If the auto-start mode fails to start the engine, in some embodimentsthe power-up sequence 1400 may proceed to optional step 1480 forreverting to a manual start. Optional step 1480 is only available onaircraft that are equipped for performing a manual start. Otherwise, ifa manual start is not an option, power-up sequence 1400 ends, and afteran appropriate cool-down period (if necessary), power-up sequence may berepeated by returning to step 1410.

The order in which steps of power-up sequence 1400 are performed may bemodified for use with different types of aircraft. For example, due toprocedures determined by a given engine manufacturer ororiginal-equipment manufacturer (OEM), or when a new or modified engineapplication is implemented, the order of steps for power-up sequence1400 may be modified.

FIGS. 15A and 15B show a flow chart for an exemplary auto-start sequence1500. Auto-start sequence 1500 may be performed using one of automaticaircraft powerplant control systems 900, 1000, 1100, or 1200 describedabove.

In a step 1510 of FIG. 15A, the auto-start system is initiated via astart switch, and the auto-start system is engaged in step 1450 asdescribed above. In an example of step 1510, a pilot activates theauto-start system for a first time by pushing a start button, which putsthe auto-start controller in a “pre-start” mode. During the pre-startmode, pressing the start button/switch does nothing to prevent prematureengine cranking. In embodiments, the start switch is engaged directly tothe starter solenoid when the auto-start system is unpowered or disabled(e.g., via a “disabled” switch).

Once the auto-start system is engaged in step 1450, the auto-startcontroller initiates the proper start sequence based on the currentengine state. Specifically, the cold-start mode is entered, auto-startsequence 1500 proceeds with a step 1520; if the hot-start mode isentered, auto-start sequence 1500 proceeds with a step 1550; and, if theflooded-start mode is entered, auto-start sequence 1500 proceeds with astep 1580.

Meanwhile, as one of the auto-start sequences is initiated, anindication that the aircraft is not yet ready to start is provided tothe pilot in a step 1512. In an example of step 1512, a “wait”indication is provided on the main flight display in the aircraftcockpit. The wait indication remains on during a “pre-start” portion ofthe auto-start mode (regardless of which auto-start mode is selected).Once the pre-start portion is complete, an indication that the aircraftis ready to start is provided to the pilot in a step 1514 of FIG. 15B.Then, a start-engine circuit is enabled (e.g., in one of steps 1532,1570, and 1586), and the start switch is activated a second time, in astep 1516. These steps are further described below in connection withtheir respective auto-start sequence.

For a cold engine start, the cold-start mode is selected in step 1520.In an example of step 1520, the auto-start controller selects thecold-start mode for the throttle control and mixture control functions.The cold-start mode includes steps 1522 to 1540 below step 1520 as shownin FIGS. 15A and 15B.

In a step 1522, the throttle control is opened to an appropriate presetposition based on the type of aircraft. In an example of step 1522, thethrottle control is set to 5% open to 10% open. In another example ofstep 1522, the throttle is fully opened.

In a step 1524, the mixture control is set to the appropriate positionbased on the type of aircraft. In an example of step 1524, the mixturecontrol is set to the “idle cutoff” position. In another example of step1524, the mixture is set to “full rich”.

In a step 1526, the fuel pump is set to “on”. For airplanes that areappropriately equipped, the fuel pump may be set to “high”. The coldauto-start sequence remains at step 1526 until the fuel pressure haspeaked. In an example of step 1526, the fuel pump is set to on/highuntil the auto-start controller verifies that the fuel flow has peaked.

In a step 1528, the fuel pump is set to “off”.

In a step 1530, the throttle control is adjusted to the “start”position. In an example of step 1530, the throttle control is set to 5%open to 10% open.

Steps 1522 through 1530 are prior to engine start and therefore may bereferred to herein as the pre-start portion of the cold auto-start mode.Following step 1530, the pre-start portion is complete and the coldauto-start sequence proceeds to a step 1514 and a step 1532, which areshown in FIG. 15B.

In a step 1514 of FIG. 15B, an indication that the aircraft is ready tostart is provided to the pilot. In an example of step 1514, the “wait”indication of step 1512 is changed to a “ready to start” indication onthe main flight display.

In a step 1532, a start-engine circuit is enabled. In an example of step1532, cranking of the engine via the start switch is enabled.

In a step 1516, the start switch is activated a second time. In anexample of step 1516, the pilot pushes and manually holds the startbutton while the starter is engaged in a step 1534 until the enginefires, then the pilot releases the start button. In another example ofstep 1516, the pilot pushes and releases the start button, and theauto-start controller automatically latches the start switch to remainactivate until the engine fires. For the automatic latching option, thepilot may press the start button again to disengage the starter andabort the auto-start sequence.

In step 1534, the engine starter is engaged. In an example of step 1534,the engine started is engaged (e.g., either manually or automaticallyfrom step 1516) until the engine cranks up to a speed of 500-RPM.

In a step 1536, the engine starter is disengaged. In an example of step1536, the starter disengages once the speed exceeds a preset value(e.g., 500-RPM or 800-RPM). For the manual option, the pilot releasesthe start button. For the automatic option, the auto-start controllerunlatches the start switch.

In a step 1538, the throttle control is adjusted to achieve the properengine idle speed. In an example of step 1538, the engine start isverified by the auto-start controller based on the engine speed (e.g.,800-RPM or 1200-RPM) and the throttle control loop is closed on apredetermined engine speed (e.g., 1200-RPM).

In a step 1540, the cold auto-start sequence ends. In an example of step1540, when the engine has successfully started, the auto-start system isdisengaged and manual throttle-control is performed by the pilot. Inanother example of step 1540, when the engine fails to start within apredetermined duration, the auto-start sequence is aborted. After apredetermined cooldown time, the start switch can be used to restart theauto-start sequence at step 1510 of FIG. 15A.

For a hot engine start, the hot-start mode is selected in step 1550 ofFIG. 15A. In an example of step 1550, the auto-start controller selectsthe hot-start mode for the throttle control and mixture controlfunctions. The hot-start mode includes steps 1552 to 1579 below step1550 as shown in FIGS. 15A and 15B.

In a step 1552, the throttle control is fully closed.

In a step 1554, the mixture control is set to the idle cutoff position.

In a step 1556, the fuel pump is turned on for a predetermined duration.For airplanes that are appropriately equipped, the fuel pump may be setto “high” for the predetermined duration. In an example of step 1556,the fuel pump is set to “on” for forty-five seconds.

In a step 1558, the fuel pump is set to “off”. Following step 1558, thehot auto-start sequence proceeds to a step 1560 and a step 1562.

In step 1560, the throttle control is set to “full open”.

In step 1562, the mixture control is set to “full rich”.

In a step 1564, the fuel pump is set to “on”. If the airplane isappropriately equipped, the fuel pump may be set to “high”. The hotauto-start sequence remains at step 1564 until the fuel pressure haspeaked. In an example of step 1564, the fuel pump is set to on/highuntil the auto-start controller verifies that the fuel flow has peaked.

In a step 1566, the fuel pump is turned off.

In a step 1568 of FIG. 15B, the throttle control is set to 5% open to10% open.

Steps 1552 through 1566 are prior to engine start and therefore may bereferred to herein as a “pre-start” portion of the hot auto-start mode.Following step 1568, the pre-start portion is complete and the hotauto-start sequence proceeds to step 1514, described above, and a step1570 described below.

In step 1570, a start-engine circuit is enabled. In an example of step1570, cranking of the engine via the start switch is enabled.

In step 1516, the start switch is activated a second time, as describedabove.

In step 1572, the engine starter is engaged. In an example of step 1572,the engine started is engaged (e.g., either manually or automaticallyfrom step 1516) until the engine cranks up to a speed of 500-RPM.

In a step 1574, the engine starter is disengaged. In an example of step1574, the starter disengages once the speed exceeds a preset value(e.g., 500-RPM or 800-RPM). For the manual option, the pilot releasesthe start button. For the automatic option, the auto-start controllerunlatches the start switch.

Following step 1574, the hot auto-start sequence proceeds to a step 1576and a step 1578.

In step 1576, the throttle control is adjusted to achieve the properengine idle speed. In an example of step 1576, the engine start isverified by the auto-start controller based on the engine speed (e.g.,800-RPM or 1200-RPM) and the throttle control loop is closed on apredetermined engine speed (e.g., 1200-RPM).

In step 1578, the fuel pump is turned on (or set to high if available)to purge the system. In an example of step 1578, the fuel pump is turnedon for five seconds.

In a step 1579, the hot auto-start sequence ends. In an example of step1579, when the engine has successfully started, the auto-start system isdisengaged and manual throttle-control is performed by the pilot. Inanother example of step 1579, when the engine fails to start within apredetermined duration, the auto-start sequence is aborted. The startswitch can then be used to restart the auto-start sequence at step 1510of FIG. 15A.

For a flooded engine start, the flooded-start mode is selected in step1580. In an example of step 1580, the auto-start controller selects theflooded-start mode for the throttle control and mixture controlfunctions. The flooded-start mode includes steps 1582 to 1596 shown inFIGS. 15A and 15B below step 1580.

In a step 1582, the throttle control is set to “full open”. The pilotmay initiate the flooded-start mode by setting the throttle control to“full open” prior to pressing the “start” switch.

In a step 1584, mixture control is set to the “idle cutoff” position.

Steps 1582 and 1584 are prior to engine start and therefore may bereferred to herein as a “pre-start” portion of the flooded auto-startmode. Following step 1584, the pre-start portion of the floodedauto-start mode is complete and the flooded auto-start sequence proceedsto step 1514, described above, and a step 1586 described below.

In step 1586 of FIG. 15A, a start-engine circuit is enabled. In anexample of step 1586, cranking of the engine via the start switch isenabled.

In step 1516, the start switch is activated a second time, as describedabove.

In step 1588, the engine starter is engaged. In an example of step 1588,the engine started is engaged (e.g., either manually or automaticallyfrom step 1516) until the engine cranks up to a speed of 500-RPM.

In a step 1590, the engine starter is disengaged. In an example of step1590, the starter disengages once the speed exceeds a preset value(e.g., 500-RPM or 800-RPM). For the manual option, the pilot releasesthe start button. For the automatic option, the auto-start controllerunlatches the start switch.

Following step 1590, the flooded auto-start sequence proceeds to a step1592 and a step 1594.

In step 1592, the throttle control is adjusted to achieve the properengine idle speed. In an example of step 1592, the engine start isverified by the auto-start controller based on the engine speed (e.g.,800-RPM or 1200-RPM) and the throttle control loop is closed on apredetermined engine speed (e.g., 1200-RPM).

Meanwhile, in step 1594, the mixture is increased to “full rich” over apredetermined duration. In an example of step 1594, the mixture isincreased to “full rich” over three seconds.

In a step 1596, the flooded auto-start sequence ends. In an example ofstep 1596, when the engine has successfully started, the auto-startsystem is disengaged and manual throttle-control is performed by thepilot. In another example of step 1596, when the engine fails to startwithin a predetermined duration, the auto-start sequence is aborted. Thestart switch can then be used to restart the auto-start sequence at step1510 of FIG. 15A.

The order in which steps of auto-start sequence 1500 are performed maybe modified for use with different types of aircraft. For example, dueto procedures determined by a given engine manufacturer ororiginal-equipment manufacturer (OEM), or when a new or modified engineapplication is implemented, the order of steps for auto-start sequence1500 may be modified accordingly.

Operational Modes

FIG. 16 is a flow diagram showing an exemplary flight-plan operationalsequence 1600, which shows the different modes of aircraft operation. InFIGS. 17-19, settings for the auto-mixture control, auto-propellorcontrol, and auto-throttle control are shown and described below basedon the aircraft modes of operation shown in FIG. 16.

In a step 1610, the aircraft is in a startup mode. In an example of step1610, the auto-start mode described in connection with FIGS. 15A and 15Bmay be in operation. Alternatively, a manual start mode may be employed.

In a step 1620, the aircraft is in a ground mode. In an example of step1620, the aircraft engine is operating and the aircraft is either idlingor taxiing.

In a step 1630, the aircraft is in takeoff mode. In an example of step1630, the aircraft is taking off from a runway.

In a step 1640, the aircraft is in climb mode. In an example of step1640, the aircraft has lifted off of the ground and is steadily climbingtowards a cruise altitude.

In a step 1650, the aircraft is in a cruise mode. In an example of step1650, the aircraft has achieved level-steady flight at a preferredcruise altitude.

In a step 1660, the aircraft is in a descent mode. In an example of step1660, the aircraft is descending from its cruise altitude.

In a step 1670, the aircraft is in an approach/landing mode. In anexample of step 1670, the aircraft is approaching a runway and touchingdown on the runway.

Transitions between the flight modes may proceed in various orders. Forexample, during flight the pilot may desire an altitude change to adjustthe aircraft's altitude. For an altitude change 1645 to raise thealtitude, the flight mode is switched from cruise mode in step 1650 backto climb mode in step 1640, and then returned to cruise mode. For analtitude change 1655 to lower the altitude, the flight mode may beswitched from cruise mode in step 1650 to descent mode in step 1660, andthen returned to cruise mode. When the aircraft is cruising at arelatively low altitude, the pilot may choose a direct transition toapproach 1665, where the mode is changed directly from cruise mode instep 1650 to approach/landing mode in step 1670, rather thantransitioning from a relatively high cruising altitude via descent mode1660. If an approach/landing in step 1670 is to be aborted for ago-around 1675, the flight mode is returned to the climb mode in step1640.

FIG. 17 is a flow diagram showing an exemplary auto-mixture controlflight-plan 1700, which shows the auto-mixture control settings based onthe different modes of aircraft operation shown in FIG. 16. Theauto-mixture control settings are determined via a mixture controller,such as mixture control servo 146 described above in connection withFIGS. 5-7.

When the aircraft is in the ground mode 1620, the auto-mixture settingis set to full rich 1720.

During takeoff mode 1630 at a low altitude 1730, the auto-mixturesetting is set to full rich 1720 or scheduled fuel flow as required bythe airplane. For example, at a low altitude 1730 (e.g., from sea levelto 4,999-ft), the auto-mixture setting is set to full rich 1720. In someaircraft, the mixture will be set based on engine fuel flow 1720. Forhigher altitude takeoff, the engine must be leaned to maintain fullpower output. During takeoff mode 1630 at a high altitude 1732, ahigh-altitude takeoff target fuel flow 1742 is set automatically. Forexample, at a takeoff altitude of 5,000-ft or higher, a high-altitudetakeoff target fuel flow 1742 is set automatically.

When the aircraft is in climb mode 1640, a climb target fuel flow 1744is set automatically. Climb target fuel flow 1744 during climb mode 1640may reduce fuel flow for efficiency while maintaining enough “rich” fuelfor cooling.

During cruise mode 1650, a cruise target fuel flow 1746 is initially setwhile cruise flight is established. For “fine” leaning of the air-fuelmixture, a lean to exhaust gas temperature (EGT) setpoint 1752 is used.For example, the fuel mixture is reduced to a predetermined EGT valuerelative to the peak EGT realized during the leaning procedure. The EGTsetpoint may be established at rich of peak 1754, at peak 1756 or atlean of peak 1758.

When the aircraft is in descent mode 1660 at low altitude 1730, theauto-mixture setting is set to full rich or schedule based on the cruiseEGT 1720. During descent mode 1660 at high altitude 1732, theauto-mixture setting is set based on the last cruise EGT 1762. Forexample, the fuel flow rate is either reduced or increased based on lastcruise EGT.

During approach and landing 1670 at low altitude 1730, the auto-mixturesetting is set to full rich or set based on an altitude schedule 1720.During approach and landing 1670 at high altitude 1732, the auto-mixturesetting is set based on an altitude schedule 1772. For example, the fuelflow rate is either reduced or increased based on the aircraft's currentaltitude.

FIG. 18 is a flow diagram showing an exemplary auto-propellor controlflight-plan 1800, which shows the auto-propellor control settings basedon the different modes of aircraft operation shown in FIG. 16.

When the aircraft is in the ground mode 1620, the auto-propellor controlis set to minimum pitch and maximum speed (RPM) 1820. In variants wherean automated engine run-up is accomplished, the propellor check 1822will exercise the propellor by reducing the control enough to realize a200-RPM drop as propellor pitch increases, then return the propellor tothe minimum pitch and maximum speed (RPM). Where an automated run-upcheck is not used, the propellor check 1822 will be accomplishedmanually by the pilot.

During takeoff mode 1630, the auto-propellor control is set to minimumpitch and maximum speed (RPM) 1820.

When the aircraft is in climb mode 1640 for a maximum climb 1840, theauto-propellor control is set to minimum pitch and maximum speed (RPM)1820. For a cruise climb 1842, the auto-propellor control is set to acruise climb pitch 1844 sufficient to obtain a specific engine RPM.

During cruise mode 1650 and the descent mode 1660, the pilot sets apreferred speed (RPM) 1850 (e.g., via a switch, knob, or digital inputfrom avionics), and the propellor pitch is automatically adjusted 1852to match the RPM setting.

Upon entering the approach and landing mode 1670, the pilot sets apreferred speed (RPM) 1850 (e.g., via a switch, knob, or digital inputfrom avionics), and the propellor pitch is automatically adjusted 1852to match the RPM setting. If the pilot selects go-around or completesthe landing 1870, the auto-propellor control is set to minimum pitch andmaximum speed (RPM) 1820. Other aspects of approach and landing may beused for auto-detection without departing from the scope hereof.

FIG. 19 is a flow diagram showing an exemplary auto-throttle controlflight-plan 1900, which shows the auto-throttle control settings basedon the different modes of aircraft operation shown in FIG. 16.

When the aircraft is in the ground mode 1620, for the auto-startsequence 1500, described above in connection with FIGS. 15A and 15B, theauto-throttle function is disengaged 1920. For example, theauto-throttle engages while the auto-start sequence 1500 is performed,then disengages at the completion of auto-start.

During takeoff mode 1630, the auto-throttle function is disengaged 1920.For takeoff, the auto-throttle is disengaged as a safety feature toprevent inadvertent reduction in thrust if a failure occurs within theauto-throttle system.

When the aircraft is in climb mode 1640, if the auto-pilot (AP) isdisconnected, the pilot will adjust the aircraft pitch attitude tomaintain airspeed with the engine at a constant thrust setting (e.g.,climb thrust mode 1944). If auto-pilot is operating in Flight-LevelChange (FLC) mode 1942, then the auto-throttle is engaged in climbthrust mode 1944. For example, in climb thrust mode 1944, throttlechanges initiated by the auto-throttle via power control lever 111 aremodified to achieve and maintain a specific engine thrust (or power).Otherwise, if the autopilot is in vertical speed (VS) mode 1946, thenthe auto-throttle is engaged in speed mode 1948. For example, in speedmode 1948, throttle changes initiated by the auto-throttle via powercontrol lever 111 are modified to achieve and maintain a specificaircraft speed.

During cruise mode 1650, when the thrust mode is set by the pilot 1952,then the auto-throttle is engaged in thrust mode 1944. Otherwise, whenthe speed mode is set by the pilot 1954, then the auto-throttle isengaged in speed mode 1948.

When the aircraft is in descent mode 1660, the auto-throttle is engagedin speed mode 1948.

During approach and landing 1670, the auto-throttle is engaged in speedmode 1948.

If a go-around 1675 is employed, then the auto-throttle is engaged inthrust mode 1944.

Many different arrangements of the various components depicted, as wellas components not shown, are possible without departing from the spiritand scope of what is claimed herein. Embodiments have been describedwith the intent to be illustrative rather than restrictive. Alternativeembodiments will become apparent to those skilled in the art that do notdepart from what is disclosed. A skilled artisan may develop alternativemeans of implementing the aforementioned improvements without departingfrom what is claimed.

It will be understood that certain features and subcombinations are ofutility and may be employed without reference to other features andsubcombinations and are contemplated within the scope of the claims. Notall steps listed in the various figures need be carried out in thespecific order described.

The invention claimed is:
 1. An automatic aircraft powerplant controlsystem, comprising: a throttle control configuration for controlling athrottle, comprising: a throttle servo mechanically coupled with anengine via a throttle control linkage, wherein the throttle servo isconfigured for adjusting a throttle valve via the throttle controllinkage; a throttle control lever communicatively coupled with thethrottle servo for providing a user input to the throttle servo; and athrottle controller communicatively coupled with the throttle servo forcontrolling the throttle servo; a dual-redundant propellor servo drivefor providing propellor control, comprising: a first propellor servomechanically coupled with the engine via a first propellor controllinkage, wherein the first propellor servo is configured for adjusting apropellor governor setting of the engine; and a second propellor servomechanically coupled with the engine via a second propellor controllinkage, wherein the second propellor servo is configured as a backup tothe first propellor servo for adjusting the propellor governor settingof the engine; and a dual-redundant mixture servo drive for controllingan air-fuel mixture, comprising: a first mixture servo mechanicallycoupled with the engine via a first mixture control linkage, wherein thefirst mixture servo is configured for providing a mixture control outputto the engine via the first mixture control linkage; and a secondmixture servo mechanically coupled with the engine via a secondpropellor control linkage, wherein the second mixture servo isconfigured for providing the mixture control output to the engine viathe second mixture control linkage.
 2. The system of claim 1, furthercomprising: a first processor communicatively coupled with the firstpropellor servo for controlling the first propellor servo; and a secondprocessor communicatively coupled with the second propellor servo forcontrolling the second propellor servo.
 3. The system of claim 2,wherein inputs are provided to the first processor and the secondprocessor via an avionics bus and the avionics bus independentlyprovides one or more of the inputs to the first processor and the secondprocessor.
 4. The system of claim 3, wherein the inputs include one ormore of throttle control commands, cylinder-head temperature, engineexhaust gas temperature, propellor speed, or fuel flow.
 5. The system ofclaim 3, wherein a position of the throttle control lever is monitoredby a sensor and a signal indicative of the position is sent to theavionics bus, whereby a pitch of the propellor is determinedautomatically via the first processor or the second processor based onthe position of the throttle control lever.
 6. The system of claim 3,wherein a position of the throttle control lever is monitored by asensor and a signal indicative of the position is to sent to the firstprocessor and the second processor for controlling a pitch and a speedof the propellor based on the position of the throttle control lever. 7.The system of claim 1, further comprising: a first communication buscommunicatively coupling a first processor with a second processor; anda second communication bus communicatively coupling the first processorwith the second processor, wherein the first communication bus and thesecond communication bus each independently provide cross-communicationbetween the first processor and the second processor forchannel-to-channel monitoring.
 8. The system of claim 1, furthercomprising a propellor speed switch communicatively coupled with thefirst processor and the second processor, wherein the propellor speedswitch is configured to receive a user input for selecting a propellorspeed range.
 9. The system of claim 3, wherein the first processor andthe second processor each receive one or more inputs from the avionicsbus, whereby the first mixture servo or the second mixture servo adjustan amount of fuel for mixing with a predetermined air flow based atleast partially on the one or more inputs.
 10. The system of claim 1,wherein the throttle controller receives inputs from an avionics bus,and the throttle controller is configured to control the throttle servofor adjusting the throttle valve based at least partially on the inputs.11. The system of claim 1, wherein the throttle servo comprises a singleservo configured to back drive the throttle control lever forcontrolling the throttle valve.
 12. The system of claim 1, wherein thefirst propellor servo and the second propellor servo are each configuredto adjust the propellor governor setting of the engine to change apropellor pitch based on a position of the throttle control lever,thereby adjusting a propellor speed for a given power output from theengine.
 13. The system of claim 1, wherein the dual-redundant propellorservo drive provides independent back up propellor control in the eventof any single failure.
 14. The system of claim 1, wherein thedual-redundant mixture servo drive provides independent back up air-fuelmixture control in the event of any single failure.
 15. The system ofclaim 1, wherein the throttle control lever is configured to provide asingle lever for pilot control of aircraft power.
 16. The system ofclaim 1, wherein the throttle control configuration is compatible withan auto-land capability.